At everyday locations, such as rooms in homes, shops, offices, conference centres, etc., that are illuminated by artificial light sources, it is generally desired to measure light characteristics, e.g., the light direction, the light collimation, and the light intensity distribution together with properties such as colour point and colour rendering index of the light, in order to be able to adapt the light settings at the location in order to, e.g., save energy or to adjust the light settings according to the needs of a particular user or users. However, prior art light sensors are unable to measure all of the desired light characteristics, require a large installation space, are expensive, etc. Further, in case a light sensor is to be integrated into a light module or fixture, it should preferably be compactly designed, inexpensive, and robust. Furthermore, a light sensor should preferably be designed such that it may be used in various applications, e.g., during ambient light conditions, in energy-efficient ambient intelligent lighting systems, etc.
In addition, a further drawback with prior art light sensors is that they generally require imaging optics, such as lenses, mirrors, beam splitters, prisms, etc., as well as image processing and/or analysis.
Furthermore, in the case of, for example, a web camera (webcam), determining the light directionality would generally require direct imaging of the source.
Hence, there is a need within the art for a compact, robust and inexpensive light sensor which can be used in various applications and enables to measure light characteristics such as the light direction, the light collimation, and the light intensity distribution.
US 2007/0139765 A1 (D1) discloses a sensor having optical elements disposed thereon and light collimating screens having three portions, each with a different oblique angle of collimation relative to a substrate.
A drawback with D1 is that only three predetermined directions of incident light can be measured, thereby achieving merely a rough estimate of the light directionality. Thus, the distribution of light cannot easily be determined using D1.